This pilot study is designed to evaluate the clinical efficacy and safety of transplanted CD34+ hematopoietic stem/progenitor cells (HSC) isolated from mobilized peripheral blood for hematologic reconstitution of patients following myeloablative chemotherapy or radiotherapy. HSC are isolated using the Baxter Isolex 300i System, which is a clinical-scale investigational device designed for high through-put enrichment of such cells from mobilized peripheral blood leukaphereses. HSC can be used for autologous or allogeneic rescue following intensive cytoreductive therapy. The therapy is targeted to patients with high risk metastatic B-cell malignancies for whom peripheral blood stem cell (PBSC) transplantation is indicated. The objective of the study is to confirm that infusion of highly-enriched HSC isolated from mobilized peripheral blood results in hematopoietic reconstitution with no unusual or unexpected toxic side effects. The duration and extent of myelosuppression as well as associated side effects will be documented and reviewed relative to historical controls transplanted with unselected mobilized peripheral blood.